Thank you for starting the discussion that
we can hopefully continue during the informal Tuesday evening meeting next
week.

Below are some of the trade-offs we went
through in coming up with the numbers for the July presentations.

40GE 4x10G (cole_03_0708)

The Munich
presentation (cole_03_0508) did not one have proposal but a range of numbers
which bracketed the multiple proposals made by several companies during prior
meetings. Our proposal was in cole_03_0308 and used the 10GE-LR link budget. TP2
and TP3 specifications have to take into account Mux and DeMux losses, and the 03_0308
proposal accounted for that mostly by increasing the transmitter output power.

The 03_0708 proposal reduced the link
budget slightly, as pre-viewed in the 03_0308 presentation by taking advantage
of today’s faster DFBs. It balanced the Mux and DeMux losses between the
transmitter and receiver. The selected max TP2 power is about at the limit
where un-cooled DFB eye safety limit control starts becoming an issue, and TIA
saturation with very low loss DeMuxes starts becoming another issue. The
resulting TP3 sensitivity has a lot of margin with respect to 10G receiver
distribution. It is our view that the proposal is fully compatible with modern
10GE-LR un-cooled DFB transmitters and PIN receivers, and will re-use existing
technology with ample manufacturing margin.

100GE 4x25G (cole_01_0708)

During the Q&A session after presentation
of cole_01_0508 in Munich,
several comments were made that the penalty allocation should be increased. We
acknowledged that we were already looking at increasing the penalty allocations
and would have an increase in a future proposal. This is along the lines of
isono_01_0708, which also proposes a modest increase in penalty allocations. Cole_01_0708
increases the penalty allocations by 0.6dB from 01_0508. This 0.6dB is accommodated
by a 0.2dB increase in transmitter output power and 0.4dB increase in receiver
sensitivity. The resulting receiver sensitivity still has reasonable margin.
Suggestions have been made to accommodate the link budget increase in other
ways, and this can be subject of our future discussions.

I look forward to further discussion next
week and over the summer to arrive at a consensus draft proposal for the
September meeting.

‘refinements’ to 4x25G 10km baseline in COLE_01_0708
which increases Rx sensitivity by 0.4dB over that proposed in COLE_01_0508
which I agreed with.

Not 100G but 40G: The budget for 10km 4x10G
COLE_03_0708 has -11.5dBm OMA Rx sensitivity per lane which is 1.1dB tougher
than the Munich
proposal COLE_03_0508 which I agreed with back in May. This seems to be taking
us further away from 10G BASE LR technology re-use.

I know these numbers are subject to change at
this stage but I’d like to understand the underlying rationale for the
proposed changes in more depth than the time for Q&A in Denver would realistically allow.

During the process of discussing draft versions of contributions for the
Denver meeting aimed at filling in the details of the 100GBASE-LR4 and ER4
optical parameter tables it has become clear that there are differing opinions
over the detailed power budgets.

Since the Task Force has not yet adopted baseline presentations for all
of its agreed objectives, it seems unlikely that there will be sufficient Task
Force meeting time available next week to enter in to detailed discussion on
optical parameter values for 100GBASE-LR4 and ER4. However, as the Editor
of the clause containing these PMDs, I will be tasked with creating the firstdraft of it during the period between theDenver
meeting and the September interim. I therefore wonder if there is any
interest in holding an informal discussionto
try to identify a set of parameter values that can be used as the basis of the
first draft so that we can minimise the number of “TBDs” it
contains.

If there is sufficient interest, I will confirm thetime andlocation
of the discussion during Tuesdays Task Force meeting.